Biochips are semiconductor devices that include biological material spotted on a substrate. The biochip functions as a sensor for a particular type of molecule, such as genes, proteins, carbohydrates, cell tissues, lipids, and the like. Biochips are capable of fast and convenient bio-chemical detection; therefore, biochips are frequently used in bio-chemical analysis applications, such as diagnostic testing both at the point of care and at a care provider location.
The biological material of a biochip is typically densely spotted onto the substrate in an organized pattern referred to as an array or matrix. The array typically has an area of approximately 1 mm2 to 40 cm2. A spot of the biological material, referred to as a bio-probe, is typically no snore than 500 μm in diameter. Often each bio-probe has a physical address within the array to enable a detection apparatus to associate a molecule sensed by the biochip with a particular one of the bio-probes. Accuracy ceded in alignment ranges between 500 nm-50 um.
Methods for spotting the biological material onto the substrate of the biochip, include contact spotting and non-contact jet printing, among other methods. In contact spotting, the bio-probes are directly spotted onto the substrate with numerous mechanical pins. In non-contact jet printing the bio-probes are “printed” onto the substrate of the biochip similar to the way in which an ink-jet printer prints an image.
To perform the contact spotting and non-contact jet printing methods described above, it is necessary to align the biochip with a post-processing device before the biological material is spotted or printed. This is because the area of the biochip configured to receive the biological material includes numerous electrodes or wells organized in an array, and each bio-probe should be deposited onto one of the electrodes.
A known method of aligning the post-processing device includes using a camera system to visually inspect the biochip fir one or more alignment marks formed on the biochip. After registering the location and the angle of the alignment marks spotting of the biological material is performed.
The above-described camera alignment method aligns the biochip with the post-processing device well enough for most applications. The camera alignment method, however, is costly to employ and results in low throughput of the biochips. Therefore, improvements in the method used to align a biochip with a post-processing device are desirable.